I'm thinking of cooking some steak and storing it for later use in a cold salad. If I cook it to medium rare and cut it into strips and store it in the firdge, will it be safe to eat later? I know any bacteria mostly grows on the surface of the meat so that should be killed when cooked, but is there a higher danger of contamination on the now exposed, less cooked surface area?

If I put it in a clean container I'm guessing the pink parts are just as prone to further contamination as the outer surface.

If kept in this condition, how long should I expect this meat to stay good for in the fridge?

What would be different if we were talking about a partially eaten steak stored for later consumption?

I'd personally send it to the fridge whole -- it's easier to cut thin when it's been chilled down, and you won't get as much moisture loss (both from bleeding out after cutting, and evaporative while in the fridge).
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JoeNov 12 '13 at 19:53

3 Answers
3

As you mention, cooking the steak to medium rare does indeed kill the bacteria on the surface of the steak which is where most of the risk of contamination exists, so immediately after you've cooked the steak, if you eat it, you're probably pretty safe unless there happened to be bad organisms living inside the meat.

Assuming that you've got a good piece of meat, with nothing terrible inside it, after you cook the meat, what you need to worry about most is bacteria that you introduce to the meat, and so to answer your question, cutting meat shouldn't affect the safety of storing meat after cooking at all (as long as you use a clean knife/cutting board).

While cooking the meat does initially kill all of the surface bacteria, the fact that the surface was once cooked doesn't really do anything to deter new bacteria from moving in and going to town on the meat. What this means is that you need to be very careful to keep meat in sanitary conditions regardless of whether the exposed surface has been previously cooked or not if you're planning to eat it without cooking it again.

So, to recap, if you take a piece of meat where all bacteria has been killed via cooking, and seal it without introducing new bacteria, you should be safe to eat it.

The one remaining issue is that we're not talking about a steak that's necessarily had all bacteria killed. There's a possibility that some bacteria survived the cooking inside the meat. If this is the case, you may be safe to eat the meat right away if there are very few of these bacteria present (depending on what they are), but the longer you wait - even if you seal the whole thing up - the longer you're giving those bacteria to multiply into large enough quantities that they can destroy the meat and/or sicken you. To avoid this, you want to put the meat in the refrigerator, as soon as possible to slow bacterial action, and eat it as soon as possible. Like John, I've had success with around 3-5 days, but it really depends on what you're starting with, so I'd highly recommend that you have a good look/sniff before you eat to see if there are any signs of spoilage and discard if so. Again, this is a risk whether you cut the meat or not, so that isn't really a factor here.

Regarding partially eaten steaks, this is just introducing one more place where bacteria can get on the steak before it's sealed up and refrigerated. I could see this being no issue (if you're cutting off a piece of the steak, and sealing/refrigerating the rest while eating), or a significant issue if you're cutting the steak with utensils that have been in your mouth, or worse, trying to store a piece of steak that's been in your mouth. In those cases you're almost certainly introducing more bacteria and decreasing the amount of time you'll have before spoilage occurs.

So, in summary, cut the meat if you like - that should make no difference. Get it sealed up as soon as possible without exposing it to anything non-sterile. Put it in the refrigerator as soon as possible. Throw it out if at any point you detect spoilage. Following these steps you should be safe to keep your leftovers for 3-5 days and only rarely need to discard spoiled food.

I generally only cook steak medium-rare, and I am able to leave the leftovers in the refrigerator for up to 6 days or so (most recommendations say 3-5 days) and have never had any issues as long as it's wrapped properly. If you just put the meat on the plate and stick it in the fridge without any cover I imagine it would spoil quicker.

Whether it's partially eaten or not should not make any difference. What is important however, is to store the steak in the refrigerator right after you've cooked it and cut it so that it doesn't sit out at room temperature for too long.

My rule of thumb is 3 days in the fridge, 3 weeks in a small freezer compartment and 3 months in a freezer. In practice, a bit longer than those times is usually fine.
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Nathan MacInnesFeb 22 '11 at 13:22

According to health regulations, bacteria doesn't grow at below 5 C, so you can store it there for a really long time without worrying about bacteria. But the meat will decompose in time regardless of bacteria.

It's just as safe if you've bitten it or dipped it in some sauce full of bacteria. The fridge doesn't actually kill them, though, so don't use it as a way to decontaminate.

Bacteria don't grow quickly... that is not the same as not growing.
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SAJ14SAJNov 12 '13 at 13:38

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@SAJ14SAJ they indeed stop growing completely at some min temp, for example Salmonella stops at 6 degrees celsius. They don't die, but they don't grow either. There are certainly bacteria which grow below 5 degrees, but these are not the most dangerous ones. This is the reason why there is the large jump between safety at 4 degrees and below (3-5 days safe) and 5 degrees and up (2-4 hours safe).
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rumtscho♦Nov 12 '13 at 13:46

@rumtscho There isn't really a disconinuity safety or the growth curves of the pathogens at 4-5 C; that is an (intentional) oversimplificiation of the regulatory and advisory authiorities because it is much simpler to understand than the true curves, which do vary by pathogen. It is much akin to saying cook meat to 165 Fm, instead of saying cook it 140 F for 30 minutes, or 155 F for 2 minutes, or 165 F for30 seconds, or 180 F for 3 seconds.... Only the first recommerndation is generally made to consumers.
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SAJ14SAJNov 12 '13 at 14:58

@rumtscho Yes, bacterial growth stops completely below a certain temperature (lag phase) where bacteria are maturing not able to divide. Since bacteria are full units the asymptotic slowdown as the temperature gets lower has a hard stop (you can't have 0.3 of bacteria growing). see bacteria growth and the graph.
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MandoMandoNov 12 '13 at 18:31